Traditional approaches to the art of soybean processing involve the use of cumbersome, expensive machinery to facilitate preparation of the soybean prior to solvent extraction. For instance, after cracking of the beans and subsequent separation of the hull from the kernel portions, the cracked kernels are steam conditioned in large pressure cookers called "bean conditioners" which are located upstream from a flaking mill.
The flaking mill machine itself is a large, expensive machine that requires considerable energy to run. It requires operator skill to maintain proper flake thickness and is the source of considerable maintenance in periodically removing and grinding the rolls. The flaking mill functions to squeeze and impart a slight shear to the steam conditioned kernels resulting in the formation of a thin metal flake having a diameter of around 0.50 inch and a thickness of about 10-16 mils.
After the meal has been flaked, the traditional approach is to route the flaked meal to a further heat processing step or directly to extraction processes. This further heat processing step may occur within a jacketed screw press conveyor with steam being injected into the working section of the conveyor. The flakes are there steam treated and are mechanically worked via action of the screw flights and breaker pins which extend radially inwardly into the space between screw flights. The flakes are also subjected to back pressure caused by the die plate at the downstream end of the screw conveyor. The meal exiting the die orifices of the screw conveyor can best be described as including dust-like particles which are combined in the form of a pellet or pellets.
After the flaked, steam treated pellets exit the second heating step, they are sent to extraction processes including extractors, desolventizer-toasters, dryer-cooler, meal grinding and meal storage stations. Basically, during these processes the meal is mixed with a solvent, such as hexane, which dissolves the soybean oil. The soybean oil-solvent mixture is then separated from the meal particles. The desired soybean oil may then be isolated from the solvent solution by conventional techniques such as distillation, etc. The meal itself is desolventized, dried and then ground and stored prior to use and/or sale.
The present inventor was faced with the problem of attempting to minimize machine asset expenditures, space requirements, and energy consumption in a soybean process. To this end, it was surprisingly discovered that good quality meal and satisfactory oil recovery could be obtained even when the flaking process was entirely eliminated. Additionally, and as a departure from certain prior art processes involving the use of a second heat treatment step after flaking, only a single heat treatment step upstream from the extraction process station was necessary.